Rubbish seen over heathland about to increase rapidly (8)
I believe the answer is:
mushroom
'rubbish' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'over heathland about to increase rapidly' is the wordplay.
'over' says the letters should be written in reverse.
'heathland' becomes 'moor' (I've seen this before).
'about' says to put letters next to each other.
'to increase rapidly' becomes 'mush' (I can't explain this - if you can you should give a lot more credence to this answer).
'moor' written backwards gives 'room'.
'room' put after 'mush' is 'MUSHROOM'.
'seen' is the link.
Can you help me to learn more?
(Other definitions for mushroom that I've seen before include "parasol, for instance" , "Fleshy fungus" , "Snowball; fungus" , "grow suddenly" , "expand rapidly" .)